Number Of New Cells Research Articles

The reproduction number and its probability distribution for stochastic viral dynamics.

We consider stochastic models of individual infected cells. The reproduction number, R, is understood as a random variable representing the number of new cells infected by one initial infected cell in an otherwise susceptible (target cell) population. Variability in R results partly from heterogeneity in the viral burst size (the number of viral progeny generated from an infected cell during its lifetime), which depends on the distribution of cellular lifetimes and on the mechanism of virion release. We analyse viral dynamics models with an eclipse phase: the period of time after a cell is infected but before it is capable of releasing virions. The duration of the eclipse, or the subsequent infectious, phase is non-exponential, but composed of stages. We derive the probability distribution of the reproduction number for these viral dynamics models, and show it is a negative binomial distribution in the case of constant viral release from infectious cells, and under the assumption of an excess of target cells. In a deterministic model, the ultimate in-host establishment or extinction of the viral infection depends entirely on whether the mean reproduction number is greater than, or less than, one, respectively. Here, the probability of extinction is determined by the probability distribution of R, not simply its mean value. In particular, we show that in some cases the probability of infection is not an increasing function of the mean reproduction number.

Self-gravity Simulation Method Based on Distance-controlled Mesh Encryption

In the space-borne gravitational wave (GW) detection mission, the self-gravity noise caused by the deformation and residual jitter of the satellite platform is an important source of the total acceleration noise. In order to estimate the magnitude of the noise, the gravity acceleration and gravity gradient at the TM need to be carefully evaluated, which requires high accuracy of the self-gravity simulation. After the satellite component is divided into several mass cells by using the grid generation technology, if the number of cells is too small, the total gravity and gravity gradient obtained by superimposing the gravity between each cell and the TM will deviate greatly from the true value. On the other hand, directly densifying all single cells will produce a large number of new cells, reducing the simulation efficiency. Aiming at these problems, we present here the self-gravity simulation method based on distance-controlled grid refinement, analysis of subdivision unit size, unit and the distance between the test quality and the relationship between the simulation error, select the appropriate scaling factor to encrypt the initial mesh. It is expected to reduce the number of units on the premise of meeting the precision requirements of self-gravity simulation and then improve the simulation efficiency. The model test shows that when the grid cells are hexahedral, compared with simulation results using uniformly mesh encryption, the accuracy of the self-gravity simulation results based on distance-controlled is an order of magnitude higher, and the total number of grid cells used is less.

Pair-bonding and social experience modulate new neurons survival in adult male and female prairie voles (Microtus ochrogaster).

Prairie voles are a socially monogamous species that, after cohabitation with mating, form enduring pair bonds. The plastic mechanisms involved in this social behavior are not well-understood. Neurogenesis in adult rodents is a plastic neural process induced in specific brain areas like the olfactory bulbs (OB) and dentate gyrus (DG) of the hippocampus. However, it is unknown how cell survival is modulated by social or sexual experience in prairie voles. This study aimed to evaluate if cohabitation with mating and/or social exposure to a vole of the opposite sex increased the survival of the new cells in the main and accessory OB and DG. To identify the new cells and evaluate their survival, voles were injected with the DNA synthesis marker 5-bromo-2’-deoxyuridine (BrdU) and were randomly distributed into one of the following groups: (A) Control (C), voles that did not receive any sexual stimulation and were placed alone during the behavioral test. (B) Social exposure (SE), voles were individually placed in a cage equally divided into two compartments by an acrylic screen with small holes. One male and one female were placed in opposite compartments. (C) Social cohabitation with mating (SCM), animals mated freely. Our findings demonstrated that SCM females had increases in the number of new cells (BrdU-positive cells) in the main olfactory bulb and new mature neurons (BrdU/NeuN-positive cells) in the glomerular layer (GlL). In contrast, these new cells decrease in males in the SE and SCM conditions. In the granular cell layer (GrL), SCM females had more new cells and neurons than the SE group. In the accessory olfactory bulb, in the anterior GlL, SCM decreased the number of new cells and neurons in females. On the other hand, in the DG, SCM and SE increase the number of new cells in the suprapyramidal blade in female voles. Males from SCM express more new cells and neurons in the infrapyramidal blade compared with SE group. Comparison between male and females showed that new cells/neurons survival was sex dependent. These results suggest that social interaction and sexual behavior modulate cell survival and influence the neuronal fate in a sex-dependent manner, in the OB and DG. This study will contribute to understand neural mechanisms of complex social and pair bond behaviors in the prairie voles; supporting adult neurogenesis as a plastic mechanism potentially involved in social monogamous strategy.

Mechanism of Neural Regeneration Induced by Natural Product LY01 in the 5×FAD Mouse Model of Alzheimer's Disease.

Background: A sharp decline in neural regeneration in patients with Alzheimer’s disease (AD) exacerbates the decline of cognition and memory. It is of great significance to screen for innovative drugs that promote endogenous neural regeneration. Cytisine N-methylene-(5,7,4′-trihydroxy)-isoflavone (LY01) is a new compound isolated from the Chinese herbal medicine Sophora alopecuroides with both isoflavone and alkaloid characteristic structures. Its pharmacological effects are worth studying. Objective: This study was designed to determine whether LY01 delays the cognitive and memory decline in the early stage of AD and whether this effect of LY01 is related to promoting neural regeneration. Methods: Eight-week-old 5×Familial Alzheimer’s Disease (5×FAD) mice were used as disease models of early AD. Three doses of LY01 administered in two courses (2 and 5 weeks) of treatment were tested. Cognition, memory, and anxiety-like behaviors in mice were evaluated by the Morris water maze, fear conditioning, and open field experiments. Regeneration of neurons in the mouse hippocampus was observed using immunofluorescence staining. The effect of LY01 on cell regeneration was also demonstrated using a series of tests on primary cultured neurons, astrocytes, and neural stem cells (NSCs). In addition, flow cytometry and transcriptome sequencing were carried out to preliminarily explored the mechanisms. Results: We found that LY01 reduced the decline of cognition and memory in the early stage of 5×FAD mice. This effect was related to the proliferation of astrocytes, the proliferation and migration of NSCs, and increases in the number of new cells and neural precursor cells in the dentate gyrus area of 5×FAD mice. This phenomenon could be observed both in 2-week-old female and 5-week-old male LY01-treated 5×FAD mice. The neuronal regeneration induced by LY01 was related to the regulation of the extracellular matrix and associated receptors, and effects on the S phase of the cell cycle. Conclusion: LY01 increases the proliferation of NSCs and astrocytes and the number of neural precursor cells in the hippocampus, resulting in neural regeneration in 5×FAD mice by acting on the extracellular matrix and associated receptors and regulating the S phase of the cell cycle. This provides a new idea for the early intervention and treatment of AD.

Anisotropic multi-level hp-refinement for quadrilateral and triangular meshes

This paper extends the multi-level hp -approach—previously introduced for the isotropic refinement of quadrilateral and hexahedral elements—to the anisotropic refinement of quadrilateral and triangular meshes. To this end, this work first introduces anisotropic split operators for the hierarchical refine-by-superposition concept. For quadrilateral cells, the well-known anisotropic h 2 -split is used. For the anisotropic refinement of triangular cells, a novel split along the barycentric mid-lines is introduced, which minimizes the number of new cells without distorting their shape. Second, it is shown that the isotropic multi-level hp -approach of handling hanging nodes is not directly applicable in the case of directional refinement. For this reason, this work analyses the requirements of a valid fe-basis on anisotropically refined, irregular multi-level meshes and by this generalizes the isotropic multi-level hp -concept. On this basis, an algorithmic realization is derived demonstrating that the applied refine-by-superposition idea carries the implementational simplicity and the native support of arbitrary irregular meshes to anisotropic refinements. A systematic study of benchmarks featuring vertex-, edge-, and edge-vertex singularities as well as boundary layers shows that these advantages come neither at the expense of the approximation quality, nor the sparsity or conditioning of the final equation system. Further, an ad hoc edge-based indication scheme is introduced that reliably guides the place and the direction of the anisotropic refinement process even on unstructured meshes. The presented results qualify the proposed approach as an automatic, anisotropic multi-level hp -refinement method for quadrilateral and triangular meshes, coming at a marginal implementational complexity and without any restrictions due to arbitrary hanging nodes and the associated dead-lock problems. • Generalization of multi-level hp-method to anisotropic refinement of triangles and quadrilaterals. • Dead-lock free directional refinement without limitations due to hanging nodes. • Formulation of an anisotropic split of triangles that is free of element distortions. • Automatically driven anisotropic refinement of unstructured, mixed meshes.

New granule cells in the olfactory bulb are associated with high respiratory input in an enriched odor environment

New neurons are constantly generated in the olfactory bulb and the dentate gyrus of the hippocampus. The number of new cells depends on sensory experiences; an enriched odor environment increases neurogenesis and neural survival. The aim of this study was to investigate whether enriched olfactory stimuli affect neurogenesis of mitral and granule cells of the olfactory bulb and dentate gyrus, and whether respiratory activity accompanied by olfactory stimuli is associated with new cells in these regions. To this end, respiratory activity during enriched odor stimuli was continuously measured in mice and new cells were stained with 5-bromo-2′-deoxyuridine, which selectively labels proliferating cells. An enriched olfactory environment significantly increased neurogenesis of mitral and granule cells in the olfactory bulb, but not in the dentate gyrus. Additionally, an increase of new granule cells under the enriched odor condition was correlated to sniffing frequency power, which had a significantly different pattern from the no-odor condition. A high respiratory frequency with frequent odor stimuli may be associated with activation of granule cells to form inhibitory neurons and this active state might increase granule cell neurogenesis.

Intellectual components of personal Soviet experience

S. S. Neretina defined the time interval between 1917 and 1991 as “Soviet dirt” [Neretina S., 2012, p. 373], and the internal politics of today's Russia as an attempt to construct a neo-Soviet state on a truncated neo-Russian space [Neretina S., 2012, p. 492]. This approach to assessing the situation in the country coincides with one of the general statements of Ernst Jünger: Governments replace each other, like segments of a tapeworm; but their head, their intelligible character, remains the same. Each new one adds a number of new cells to the existing prison. The art of public administration is increasingly reduced to the ability, with all that, to create the illusion of freedom, and, therefore, along with the police, propaganda becomes the main tool [Yunger E., 2007, p. 202]. Hence, the identification and description of the entire variety of forms of intellectual support for the relationship of the illusion of freedom with police and propaganda activities becomes an important task of humanitarian knowledge. In this article I will try to load the given definitions and statements with my own experience of comprehending them passed through the reflections of some contemporaries

Abstract P111: Effects Of Magnetic Field On Abca1-mediated Cellular Lipid Release And Adult Brain Cell Generation In Mice

Aim: This project aims to explore a novel magnetic field (MF) health care based on the cholesterol metabolism. Methods: Mouse peritoneal macrophages foam cells were incubated in CO 2 -independent culture medium containing apoA-I and were exposed in a MF (0.4 T) using the electromagnet of EPR spectrometer. C57BL/6N mice (8 week-old) were peritoneally injected F-ara-EdU (133μg/g mouse body weight) then exposed to MF under the identical condition. Mouse plasma, cerebrospinal fluid, liver and brain were harvested on the 28 th day. Lipoprotein profiles were examined enzymatic detection followed by a gel-permeable-HPLC (Skylight Biotech Inc.). Amyloid β40 and β42 levels were determined by WAKO ELISA kit. Fixed mouse brain sections (40um) were prepared by Leica CM1900 cryostat. Alexa fluor® 488 conjugates were link to F-ara-EdU by a click chemistry method and fluor positive nucleus images were captured by a confocal super resolution SpinSR10 (Olympus, Inc.). Results: ABCA1-apoA-I mediated cellular cholesterol release was not affected or reduced by the exposure in the MF of 0.4 T. The Pcsk9 expression showed significant reduction in the hepatocytes. Reduction of Abca1 expression and increase of Scarb1 were obtained non significantly. The newly generated hippocampal dentate gyrus cells in the control mice group and the MF exposed group were 1.6±1.17, and 0.47±0.62 cells per dentate gyrus section, respectively (P=0.003) despite bulk of new cells in olfactory bulbs in the both groups. Discussions: No substantial increase in cellular cholesterol export was observed by MF irradiation of mouse peritoneal macrophage cells. In addition, the lipoprotein profile showed a decrease in HDL cholesterol even after 28 days. As a result of gene expression in the liver, a decrease in ABCA1 expression and an increase in SR-BI expression inferred reduction of HDL. The number of new cells detected in the granular zone and the subgranular zone in the dentate gyrus of the hippocampus was significantly reduced in the mice subjected to the MF treatment. In the future, it is necessary to investigate in detail whether these newborn cells are neuron or glial cells.

Housing experience affects adult neurogenesis in turtles (Chrysemys picta).

Adult neurogenesis increases in mammals when they are exposed to an enriched environment or given the opportunity to exercise. In this experiment, we investigated whether turtles would show differences in the number of new neurons in the telencephalon when they were exposed to deep water, conspecifics, and plants and logs (EE group), compared to a group of animals housed in individual cages with shallow water (IN group). A control group (EX) was given deep water and conspecifics but no plants and logs. We gave nine injections of BrdU over a 3-week period, starting when the turtles were introduced to the housing. The results showed that both the EE and the EX groups had more new cells in the dorsal ventricular ridge (DVR), a sensory area of the telencephalon. The two groups did not differ from one another. The group-housed animals also had a higher percentage of new neurons in the DVR that were double labeled for NeuN, a marker of neurons, compared to the IN group. There were no significant differences between groups in the number of new cells in the medial cortex, the homolog of the hippocampus. These findings demonstrate that the housing experience influences the number of new cells that survive in the brains of turtles. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Effects of Mating and Social Exposure on Cell Proliferation in the Adult Male Prairie Vole (Microtus ochrogaster).

Microtus ochrogaster is a rodent with a monogamous reproductive strategy characterized by strong pair bond formation after 6 h of mating. Here, we determine whether mating-induced pair bonding increases cell proliferation in the subventricular zone (SVZ), rostral migratory stream (RMS), and dentate gyrus (DG) of the hippocampus in male voles. Males were assigned to one of the four groups: (1) control: males were placed alone in a clean cage; (2) social exposure to a female (SE m/f): males that could see, hear, and smell a sexually receptive female but where physical contact was not possible, because the animals were separated by an acrylic screen with small holes; (3) social exposure to a male (SE m/m): same as group 2 but males were exposed to another male without physical contact; and (4) social cohabitation with mating (SCM): males that mated freely with a receptive female for 6 h. This procedure leads to pair bond formation. Groups 2 and 3 were controls for social interaction. Male prairie voles were injected with 5-bromo-2′-deoxyuridine (BrdU) during the behavioral tests and were sacrificed 48 h later. Brains were processed to identify the new cells (BrdU-positive) and neuron precursor cells (neuroblasts). Our principal findings are that in the dorsal region of the SVZ, SCM and SE m/f and m/m increase the percentage of neuron precursor cells. In the anterior region of the RMS, SE m/f decreases the percentage of neuron precursor cells, and in the medial region SE m/f and m/m decrease the number of new cells and neuron precursor cells. In the infrapyramidal blade of the subgranular zone of the DG, SE m/m and SCM increase the number of new neuron precursor cells and SE m/m increases the percentage of these neurons. Our data suggests that social interaction, as well as sexual stimulation, leads to pair bonding in male voles modulating cell proliferation and differentiation to neuronal precursor cells at the SVZ, RMS, and DG.

Puasa Selama Kebuntingan terhadap jumlah sel neuron Cereberum dan Cerebellum Rattus norvegicus Baru Lahir

Fasting by pregnant women causes increasing neurons in the brain. An increasing number of neuron cells will speed up information processing, so it is expected to increasing intelligence. The purpose of this study was to analyze the effect of fasting during pregnancy on the number of new cells of the cerebrum neuron and the newly born Rattus norvegicus cerebellum. The research design was true experimental laboratory posttest only with control group design. Pregnant Rattus norvegicus samples consisted of 3 groups and 1 control group with a total sample of 32 divided by 4; Xo control group without fast treatment, fasting X1 group in 1st trimester (2 days), fasting X2 group in 2nd trimester (2 days), fasting group X3 at TM 3 (2 days). Data analysis using Shapiro – Wilk normality test, followed by ANOVA test and using SPSS for Windows 23 software. The results of statistical analysis showed no significant difference in the number of cerebrum neuron cells in the four groups P = 0.210 (p> 0.05) and there were significant differences in the number of cerebrum neuron cells in the four groups P = 0.032 (p <0.05). The conclusion of this study is there was no difference in the number of neuron cells in cerebrum and cerebellum of Rattus norvegicus newborn in the fasting mother 2 days during trimester I, II dan III of pregnancy. There was a difference in the number of neuron cells in the new cerebellum of Rattus norvegicus fasting for 2 days during trimester III of pregnancy, and there were differences the effect of the number of neuron cell in cerebellum of Rattus norvegicus in all groups.

Repeated Paced Mating Increases the Survival of New Neurons in the Accessory Olfactory Bulb.

In female rats, the first sexual experience under paced mating conditions increases the number of newborn cells that migrate into the granular layer of the accessory olfactory bulb (AOB). Repeated paced mating has a potentiating effect on the number of new neurons that migrate to the AOB compared with a single session 15 days after paced mating. On the other hand, one paced mating session does no increases the survival of new cells 45 days after mating. In the present study, we evaluated if four paced mating sessions could increase the survival of new neurons in the AOB and main olfactory bulb (MOB) 45 days after females mated. Sexually naive female rats were ovariectomized, hormonally supplemented and randomly assigned to one of five groups: (1) Control, no sexual contact (C); (2) Four sessions in which females were exposed, without mating, to a sexually experience male rat (SE); (3) One session of paced mating (PM1); (4) Four sessions of paced mating (PM4); and (5) Four sessions of non-paced mating (NPM4). In the first behavioral test, females received the DNA synthesis marker 5-bromo-2′deoxyuridine and were euthanized 45 days later. Our data showed that the number of new cells that survived in the mitral cell layer of the AOB decreased when females were exposed to a sexually active male, in comparison to females that mated once pacing the sexual interaction. Repeated sexual behavior in pacing conditions did not increase the survival of new cells in other layers of the MOB and AOB. However, a significant increase in the percentage of new neurons in the granular and glomerular layers of the AOB and granular layer of the MOB was observed in females that mated in four sessions pacing the sexual interaction. In the group that paced the sexual interaction for one session, a significant increase in the percentage of neurons was observed in the glomerular layer of the AOB. Our data suggest that repeated paced mating increases the percentage of new neurons that survive in the olfactory bulb of female rats.

Exponential growth of branching processes in a general context of lifetimes and birthtimes dependence

We study the exponential growth of branching processes with ancestral dependence. We suppose here that the lifetimes of the cells are dependent random variables, that the numbers of new cells are random and dependent. Lifetimes and new cells’s numbers are also assumed to be dependent. Applying the spectral study of Laplace-type operators recently made in Hervé et al. [ESAIM: PS 23 (2019) 607–637], we illustrate our results in the Markov context, for which the exponential growth property is linked to the Laplace transform of the lifetimes of the cells.

The First Mating Experience Induces New Neurons in the Olfactory Bulb in Male Mice

In rodents, neurogenesis in the olfactory bulbs (OBs) is enhanced by exposure to olfactory enriched environments including sexually relevant odors. In the present study we evaluated whether sexual stimulation in male mice increases the number of newly generated cells that reach the OB and whether these cells differentiate into neurons. To this end, we used sexually naive male C57BL mice randomly assigned to one of three groups: (1) control, in which animals were left alone in their home cages; (2) exposure, in which animals were exposed to a receptive female precluding any physical contact; and (3) mating, in which males copulated with females. Males were given three injections of the DNA synthesis marker 5-bromo-2′-deoxyuridine (BrdU) 2 h before, at the end and 2 h after the test. Fifteen days after BrdU administration, brains were removed and processed to identify new cells and evaluate if they had differentiated into neurons in the granular (GR), mitral (MI) and glomerular (GL) cell layers of the main and accessory OB (MOB and AOB, respectively). We found an increase in the percentage of new cells that differentiate into neurons in the GL cell layer of the MOB of males from the mating group compared with those from the exposure and control groups. No differences were found in the number of new cells or percentage of new neurons in the rest of the analyzed regions. In male mice, the first sexual experience increases the percentage of new cells that differentiate into neurons in the GL cell layer of the MOB.

Hippocampal granule cell loss in human chronic alcohol abusers

Chronic alcohol abuse causes cognitive impairments associated with neurodegeneration and volume loss in the human hippocampus. Here, we hypothesize that alcohol reduces the number of granule cells in the human dentate gyrus and consequently contribute to the observed volume loss. Hippocampal samples were isolated from deceased donors with a history of chronic alcohol abuse and from controls with no alcohol overconsumption. From each case, a sample from the mid-portion of hippocampus was sectioned, immunostained for the neuronal nuclear marker NeuN, and counter stained with hematoxylin. Granule cell number and volume of granular cell layer in the dentate gyrus were estimated using stereology. We found a substantial reduction in granule cell number and also a significantly reduced volume of the granular cell layer of chronic alcohol abusers as compared to controls. In controls there was a slight age-related decline in the number of granule cells and volume of granular cell layer in line with previous studies. This was not observed among the alcoholics, possibly due to a larger impact of alcohol abuse than age on the degenerative changes in the dentate gyrus. Loss of neurons in the alcoholic group could either be explained by an increase of cell death or a reduced number of new cells added to the granular cell layer. However, there is no firm evidence for an increased neuronal death by chronic alcohol exposure, whereas a growing body of experimental data indicates that neurogenesis is impaired by alcohol. In a recent study, we reported that alcoholics show a reduced number of stem/progenitor cells and immature neurons in the dentate gyrus, hence that alcohol negatively affects hippocampal neurogenesis. The present results further suggest that such impairment of neurogenesis by chronic alcohol abuse also results in a net loss of granule cells in the dentate gyrus of hippocampus.

A STEREOLOGICAL STUDY OF HIPPOCAMPUS IN EXPERIMENTAL EPILETIC RAT MODEL TREATED WITH ACORUS CALAMUS AND BETA-ASARONE

Objective: Epilepsy is the fourth most prevalent neurodegenerative disorder that affects about 1–2% of people round the world. Epilepsy cannot be cured even with modern medication, but the medications can control the seizures. Even this cannot be achieved in nearly 30% of epileptic population. At this point, we felt the need of some natural supplements to protect the nervous system against neurodegeneration and so created an equivalent model of epilepsy with kainic acid lesion and studied the novel role of Acorus calamus in protecting the neurons.Methods: For this study, we divided the animals into four groups, based on the drugs used. We also produced a stereotaxic model of epilepsy by inducing kainic acid into the right hippocampus of all the animals except CO (control) group. Then, we conducted a stereological study both on the 2nd and 7th day after surgery, to rule out the neuroprotective and neuroregenerative ability of the drugs employed.Results: The results were amazing. Stereological study on the 2nd day revealed a very large lesion on the hippocampus of lesion control (LC) animals, and the lesion was very much smaller in both drug group animals. On the 7th day also the LC animals showed a large lesion, but the lesion on the drug group animals diminished due to a number of new cells, probably of neurons grown in the place of lesion.Conclusion: The results proved the neuroprotective and regenerative ability of both drugs, but as a fact, beta-asarone had an upper hand in this study.

Incorporation of new neurons in the olfactory bulb after paced mating in the female rat

One of the regions that constantly produces neurogenesis in the adult brain is the subventricular zone (SVZ), whose new cells migrate to the olfactory bulbs (OB). When the females regulate the copulatory events (paced mating) the number of new cells in the SVZ increases, as well as those observed in the OB 15 days later. However, no changes were observed in the number of cells 45 days after the females paced the sexual interaction. Constant sensory stimulation is an important promoter of cell survival in the OB circuit. Hence, we increased the number of mating sessions in this study to cover the period where stimulation of the new cells is critical for their incorporation into pre-existing circuits in the OB. Ovariectomized female Wistar rats, were injected with the mitotic marker 5-bromo-2′-deoxyuridine (BrdU, 100 mg/kg, per injection) before, at the end and one hour after mating. Sexual behavior was recorded for 1 h in 10 weekly sessions. After the last mating session, brain sections were processed to determine BrdU immunoreactivity. Our results indicate that females that paced the sexual interaction for 10 sessions had a higher number of cells in the glomerular layer (GL) of the accessory olfactory bulb (AOB) and a higher number of neurons in the granular layer (GrL) of the main olfactory bulb (MOB) in comparison to the control group. These results indicate that continued sexual interaction contributes to the integration of new cells and neurons, induced in the first sexual experience, into pre-exiting circuits of the OB.

In situ visualization on formation mechanism of bi-modal foam via a two-step depressurization approach

The formation mechanism of bi-modal foams containing cells of a relatively large size and those of a small size prepared by a two-step depressurization approach was studied through in situ visualization. The results demonstrate that the cells produced by the first depressurization do not coalesce into larger cells but shrink spontaneously in the pressure holding stage. In the second depressurization, a large number of new cells nucleate and grow into the smaller cells, driven by diffusion; meanwhile, after the holding stage, the remaining cells again expand and evolve into the final larger cells, driven by hydrodynamic forces. Based on the above mechanism, increasing the dense of large cells can be achieved by increasing the depressurization degree or reducing the holding time while an introduction of inorganic particle or an enhancement of intermediate pressure is propitious to form denser small cells.

Neurogenesis in the olfactory bulb induced by paced mating in the female rat is opioid dependent.

The possibility to control the rate of sexual stimulation that the female rat receives during a mating encounter (pacing) increases the number of newborn neurons that reach the granular layer of the accessory olfactory bulb (AOB). If females mate repeatedly, the increase in the number of neurons is observed in other regions of the AOB and in the main olfactory bulb (MOB). It has also been shown that paced mating induces a reward state mediated by opioids. There is also evidence that opioids modulate neurogenesis. In the present study, we evaluated whether the opioid receptor antagonist naloxone (NX) could reduce the increase in neurogenesis in the AOB induced by paced mating. Ovariectomized female rats were randomly divided in 5 different groups: 1) Control (not mated) treated with saline, 2) control (not mated) treated with naloxone, 3) females that mated without controlling the sexual interaction (no-pacing), 4) females injected with saline before pacing the sexual interaction and 5) females injected with NX before a paced mating session. We found, as previously described, that paced mating induced a higher number of new cells in the granular layer of the AOB. The administration of NX before paced mating, blocked the increase in the number of newborn cells and prevented these cells from differentiating into neurons. These data suggest that opioid peptides play a fundamental role in the neurogenesis induced by paced mating in female rats.

Inhibiting Production of New Brain Cells during Puberty or Adulthood Blunts the Hormonally Induced Surge of Luteinizing Hormone in Female Rats.

New cells are added during both puberty and adulthood to hypothalamic regions that govern reproduction, homeostasis, and social behaviors, yet the functions of these late-born cells remain elusive. Here, we pharmacologically inhibited cell proliferation in ventricular zones during puberty or in adulthood and determined subsequent effects on the hormone-induced surge of luteinizing hormone (LH) in female rats. Initial neuroanatomical analyses focused on verifying incorporation, activation, and pharmacological inhibition of pubertally or adult born cells in the anteroventral periventricular nucleus (AVPV) of the hypothalamus because of the essential role of the AVPV in triggering the preovulatory LH surge in females. We first showed that approximately half of the pubertally born AVPV cells are activated by estradiol plus progesterone (P) treatment, as demonstrated by Fos expression, and that approximately 10% of pubertally born AVPV cells express estrogen receptor alpha (ERα). Next, we found that mitotic inhibition through intracerebroventricular (ICV) administration of cytosine β-D-arabinofuranoside (AraC), whether during puberty or in adulthood, decreased the number of new cells added to the AVPV and the suprachiasmatic nucleus (SCN), and also blunted and delayed the hormone-induced LH surge. These studies do not prove, but are highly suggestive, that ongoing postnatal addition of new cells in periventricular brain regions, including the AVPV and SCN, may be important to the integrity of female reproduction.